This invention is directed to certain cobalt chelates and to an improved process for forming cobalt chelates and in particular, to alkyl cobalt (III) dioximates and a process that provides an improved yield and purity of such dioximates.
Cobalt chelates have been widely used in the polymerization of high and low molecular weight polymers, and in the formation of oligomers, macromoners, and latices. Also, cobalt (II) chelates have been used as chain transfer agents in free radical polymerizations to form polymers. Acrylic graft copolymers having an acrylic copolymer core and macromonomers grafted thereto have been prepared utilizing cobalt chelates. The synthesis of terminally unsaturated oligomers and functionalized diene oligomers using cobalt chelate catalysts also are known.
G. N. Schrauzer, Wingassen, J. Am. Chem. Soc 89(1967)1999, shows the formation of an alkyl chelate, i.e., an alkyl cobalt (III) dioximate, using dimethylglyoxime but the yield was low (45%) and purity less than 80%. The method when used with other glyoximes such as diphenylglyoxime, methylcarboxyethylglyoxime and methyldiphenylglyoxime did not form an alkyl cobalt (III) dioximate. There is a need for a process that will produce an alkyl cobalt (III) dioximate in a high yield and in a high purity. The process should allow for the formation of alkyl cobalt (III) dioximates by using glyoximes other than dimethylgloxime since such other glyoximes can impart important properties to the chelate, such as shelf stability and solubility in a variety of solvents. Such properties make the chelate more versatile and useful and cost effective in polymerization processes used for a variety of monomers.